Acetic Anhydride (Ac.sub.2 O) is a chemical that has many uses. For example, it is used in the manufacture of cellulose acetate from cellulose. Acetic anhydride is prepared by the carbonylation of methyl acetate (MeOAc) in the presence of a homogeneous Rh catalyst with a lithium iodide (Lil) promoter. Others have attempted to design heterogeneous catalysts with a view of minimizing the leaching of the metal complex. One such system described in U.S. Pat. No. 4,328,125 is an anion exchange resin to which is ionically bound an anionic metal carbonyl species having the general formula M.sub.n (CO).sub.m (X).sub.p.sup.-, where M is a transition metal. These catalysts have been described and used for the carbonylation of alcohols for the production of carboxylic acids.
Marston et al. in U.S. Pat. No. 5,155,261 and Minami et al. in U.S. Pat. No. 5,364,963 have described a similar catalyst consisting of a cross-linked 4-vinylpyridine divinylbenzene copolymer containing quaternized pyridine groups supporting a rhodium species. This catalyst is robust and offers higher operating temperature for the carbonylation of methanol to acetic acid. U.S. Pat. No. 5,360,929 discloses the use of these catalysts to produce carboxylic acid anhydrides from carboxylate esters and ethers.